Move misplaced assignment in num_sign_bit_copies1

The old assignment to bitwidth was before we handled VOIDmode with:

      if (mode == VOIDmode)
        mode = GET_MODE (x);

so when VOIDmode was specified we would always use:

      if (bitwidth < GET_MODE_PRECISION (GET_MODE (x)))
        {
          num0 = cached_num_sign_bit_copies (x, GET_MODE (x),
                                             known_x, known_mode, known_ret);
          return MAX (1,
                      num0 - (int) (GET_MODE_PRECISION (GET_MODE (x)) - bitwidth));
        }

For a zero bitwidth this always returns 1 (which is the most
pessimistic result).

gcc/
2016-11-15  Richard Sandiford  <richard.sandiford@arm.com>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* rtlanal.c (num_sign_bit_copies1): Calculate bitwidth after
	handling VOIDmode.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r242440

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f5ab2f3275fb516b3c8654b6943084c15dbc57cc..95e3dc5047c5ea32cca663f0cf32dc0d9bb3d086 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2016-11-15  Richard Sandiford  <richard.sandiford@arm.com>
+           Alan Hayward  <alan.hayward@arm.com>
+           David Sherwood  <david.sherwood@arm.com>
+
+       * rtlanal.c (num_sign_bit_copies1): Calculate bitwidth after
+       handling VOIDmode.
+
 2016-11-15  Matthias Klose  <doko@ubuntu.com>
 
        * doc/install.texi: Remove references to gcj/libjava.

diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c
index 4617e8ee449d62da3217f285c5a0e35846fcdfaa..e08f2be789b9a7394673216f4c50cc219a31cce8 100644 (file)
--- a/gcc/rtlanal.c
+++ b/gcc/rtlanal.c
@@ -4795,7 +4795,6 @@ num_sign_bit_copies1 (const_rtx x, machine_mode mode, const_rtx known_x,
                      unsigned int known_ret)
 {
   enum rtx_code code = GET_CODE (x);
-  unsigned int bitwidth = GET_MODE_PRECISION (mode);
   machine_mode inner_mode;
   int num0, num1, result;
   unsigned HOST_WIDE_INT nonzero;
@@ -4811,7 +4810,8 @@ num_sign_bit_copies1 (const_rtx x, machine_mode mode, const_rtx known_x,
       || VECTOR_MODE_P (GET_MODE (x)) || VECTOR_MODE_P (mode))
     return 1;
 
-  /* For a smaller object, just ignore the high bits.  */
+  /* For a smaller mode, just ignore the high bits.  */
+  unsigned int bitwidth = GET_MODE_PRECISION (mode);
   if (bitwidth < GET_MODE_PRECISION (GET_MODE (x)))
     {
       num0 = cached_num_sign_bit_copies (x, GET_MODE (x),